Delete comment from: Ken Shirriff's blog
I think I have an idea about why the voltage sagged on the good chargers-
The device's charge controller obviously dissipates the most heat when charging in the CC phase with the highest current right? when the voltage sags in this situation, the pass transistor has to drop less voltage across itself to regulate the current and hence doesn't dissipate as much heat.
May 2, 2015, 3:10:27 PM
Posted to A dozen USB chargers in the lab: Apple is very good, but not quite the best